This application claims priority under 35 U.S.C. xc2xa7xc2xa7119 and/or 365 to 2000-290239 filed in Japan on Sep. 25, 2000; the entire content of which is hereby incorporated by reference.
1. Field of the Invention
The present invention relates to a copper source liquid for use in MOCVD (metal organic chemical vapor deposition) processes that produce copper-containing films on substrates by CVD. The invention also relates to a method for producing this copper source liquid.
2. Description of the Related Art
Aluminum and aluminum alloys are most often used as the material in the electrodes and interconnects in semiconductor devices. Copper, on the other hand, is used as a component in the electrode and interconnect layers, for example, as the material of barrier layers, and is used as an alloying component with aluminum. In addition, rapid progress has recently been made toward the realization of copper interconnects as a replacement for aluminum interconnects.
Vapor deposition and sputtering are the methods generally used to form copper and copper alloy films on semiconductor wafers. Very recently, however, technology has been developed that enables the formation of copper and copper alloy films by MOCVD. (Hexafluoroacetylacetonato)copper(I)xc3x97trimethylvinylsilane (chemical formula: (O2C5HF6) Cuxc3x97(CH3)3SiCHxe2x95x90CH2) is typically used as the copper source liquid. This copper source liquid is stored in the liquid phase in a storage means, transported from the storage means through a vaporizer, and, after conversion into vapor form, is supplied to the treatment compartment holding the treatment substrate and is employed therein for film formation. A small amount of water is added to the aforementioned copper source liquid in order to promote decomposition during the film-formation process and thereby raise the film-formation rate and to improve the adherence between the CVD film and substrate. This water addition has been carried out within the treatment compartment or immediately upstream therefrom since the addition of water to the subject copper source liquid has resulted in rapid decomposition of the copper source liquid with a corresponding decline in its quality. Water addition in this manner also results in a reduced level of control with regard to the quantity of water added to the copper source liquid, which in turn causes a diminished reproducibility on the part of CVD film quality.
This invention was developed in view of the foregoing problems with the prior art. The object of this invention is to improve the reproducibility of CVD film quality by improving the capacity to control the amount of water added to the copper source liquid used in MOCVD processes.
In a first embodiment, the present invention provides a copper source liquid for MOCVD processes (hereafter referred to as MOCVD copper source liquid) that characteristically comprises a copper source component and water, wherein the source component comprises at least 90 weight % of a substance with the chemical formula (1)
(O2C5HF6)Cuxc3x97Lxe2x80x83xe2x80x83(1)
in which L is an electrically neutral organic ligand that contains a carbon-carbon multiple bond whose p-electrons participate in coordination bonding with the monovalent copper; and the dissolved oxygen concentration in the water is no more than 0.5 ppm relative to the water.
In a second embodiment, the present invention provides a MOCVD copper source liquid according to the first embodiment, characterized in that the proportion of water in the copper source liquid is no more than 10 weight %.
In a third embodiment of the present invention, a MOCVD copper source liquid according to the first or second embodiment is provided, characterized in that the source component contains less than 10 weight % L of chemical formula (1) separate from the aforesaid substance with chemical formula (1).
In a fourth embodiment, the present invention provides a MOCVD copper source liquid according to any of the first to third embodiment, characterized in that L in chemical formula (1) is an organic ligand selected from the group consisting of trimethylvinylsilane, allyltrimethylsilane, vinyltrimethoxysilane, triethoxyvinylsilane, dimethoxymethylvinylsilane, vinylcyclohexane, 2-methyl-1-hexen-3-yne, 3,3-dimethyl-1-butene, and 1,5-cyclooctadiene.
In a fifth embodiment, the present invention provides a MOCVD copper source liquid according to any of the first to third embodiments, characterized in that L in chemical formula (1) is R3Si(CH2)nCHxe2x95x90CH2 wherein the subscript n is zero or a positive integer and R denotes alkyl or alkoxyl.
In a sixth embodiment, the present invention provides a MOCVD copper source liquid according to any of the first to third embodiments, characterized in that L in chemical formula (1) is R2Cxe2x95x90CH2 wherein R is H or hydrocarbyl.
In a seventh embodiment of the present invention, the present invention provides a MOCVD copper source liquid according to any of the first to third embodimients, characterized in that L in chemical formula (1) is (CH3)3SiCHxe2x95x90CH2.
In another embodiment of the present invention, there is provided a method for producing MOCVD copper source liquid according to any of the first to seventh embodiments, said method comprising
a process in which the oxygen dissolved in the water is removed by mixing the water and a deoxygenating agent with a compound of chemical formula (1) to form a liquid mixture and stirring the liquid mixture,
a process in which, after completion of stirring of the liquid mixture, the water is separated from the deoxygenating agent and is recovered, and
a process in which the aforementioned substance of chemical formula (1) and the water recovered from the liquid mixture are mixed in order to form the copper source liquid.
In a ninth embodiment of the present invention, there is provided a method for producing MOCVD copper source liquid according to any of the first to seventh embodiments, said method characteristically comprising
a process in which an inert gas is bubbled through water in order to remove the oxygen dissolved in the water, and
a process in which the copper source liquid is formed by mixing the bubbling-treated water with the aforementioned substance of chemical formula (1).
The aforementioned embodiments of this invention explore a variety of executions of this invention, and various embodiments of this invention can be derived by suitable combination of a plural number of disclosed constituent elements. For example, when an embodiment of the present invention has been derived by omitting some constituent elements from the overall set of constituent elements presented for the embodiment, these omitted elements can be suitably fulfilled by conventional well-known technologies in the actual working of the derived inventive embodiment.